Determination of fluid movement in bore holes



Jan. 13, 1959' A. c. NESTLE DETERMINATION OF FLUID MOVEMENT IN BORE HOLES Filed June l 1954 www DETERMINATION OF FLUID MOVEMENT IN BORE HOLES Alfred C. Nestle, Houston, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Dela- Ware Application .lune 1, 1954, Serial No. 433,685 Claims. (Cl. 25E- 1.8)

This invention relates to the determination of the movement of iluid in bore holes and more particularly, to the direction of movement of drilling fluid, which is used in the drilling or boring of the hole. The principal object of the invention is the provision of a method and an apparatus through the use of which a determination may be made as to the location of a zone of lost circulation, into which the drilling fluid is passing and thereby being lost. j

It is well known that in the drilling of bore holes the problem of'lost circulation of drilling fluid is a very important one. The drilling fluid or mud which is circulated down through the drill string or pipe serves the purpose of lubricating the bit While it is doing its cutting, removing and circulating upwardly to the surface the cuttings formed in the boring of the hole, and plastering or coating of the walls of the hole with a mud cake, this cake serving to prevent sloughing of the formations into the hole. It is obvious that whenv anything happens to prevent the proper circulation of this drilling mud through the hole, the drilling of the hole is retarded, and it may be necessary to stop the operations completely. It is not infrequent that, in drilling a bore hole, a zone or formation is traversed by the drill bit, which zone is so porous and permeable that a great deal, if not all, of the drilling fluid passes into this zone and outwardly into the formation instead of returning to the surface, and thereby becoming lost. It is for this reason that these zones are frequently termed zones of lost circulation. When such a zone of lost circulation has been accurately located, steps may be taken to remedy the situation, as by cementing off the exposed walls of the formation, by forcing a plugging material into the formation, etc.

Another object of the invention is the provision of a method which can be carried out while the drill pipeis Within the bore hole and without any necessity of removing it therefrom.

In accordance with this invention, a small amount of a tracer fluid such as a radioactive substance is injected into the mud stream within the lower portion of the drill pipe and, preferably, just above the drill bit. Means are provided for measuring the radioactivity of the iluid surrounding the drill pipe at a point vertically spaced from the point where the injection of radioactive iluid is made. vAssuming that the drill bit is positioned opposite or directly above the upper boundary of the zone of lost circulation, t the radioactive uid injected into the mud stream will intermingle with the drilling mud and the mixture will pass downwardly or outwardly into the porous zone. The radiation detecting means spaced above the point where the radioactive fluid is injected into the mud will, therefore, not show any increase in radioactivity. Assuming, however, thattthe zone of lost circulation is above the drill bit, the mud, which has been made radioactive by the injection thereinto of the radioactive substance, will pass upwardly through the hole around the drill pipe and pastthe radiation detecting means on its way to the zone of lost circulation. Since the fluid surrounding the detecting means will then be radioactive, the detecting means will show an increase in radioactivity, and the operator will be apprised that the porous zone or zone of lost circulation is above the` drill bit rather than below it.

After a determination has been made as to whether the porous zone into which the drilling fluid is passing is below or above the drill bit, the drill string canbe raised or lowered, and another amount of the radioactive fluid again injected into the drilling mud stream. After this operation has been repeated a few times, the operator will know that the porous zone is at a certain position with respect to the drill bit, i. e., either just below the bit or a short distance above it. Remedial steps can then be taken to remedy this situation, as by plugging or cementing the walls of the zone.

In carrying out the method of the invention in one form an elongated tubular device or housing is lowered through the drill pipe until it rests within the lower portion of the pipe, directly above the drill bit. A quantity of a radioactive fluid, such as, for example, radioactive iodine, is disposed within the vlower end of the housing and is connected with the exterior thereof by means of a small pipe containing a valve which may be controlled by means of arsolenoid, the solenoid being controlled, in turn, by a suitable clockwork mechanism, or the like. Within the upper portion of the housing is a radiation detector capable of detecting the radiation in the uid surrounding the drill pipe. The detector may be connected to the surface by means of a conductor cable, and an indication or a record can. thus be made at'the surface of the output of the detector. As stated above, when the zone of lost circulation is above the drill bit and the instrument housing, the radioactive drilling mud surrounding the drill pipe will cause an increase in the output of the detector, and this will be observed at the surface, notifying the operator that the zone of lost circulation is above rather than below the drill bit.

In a modification a core` drill bit may be used whereby an opening is provided through the bit to permit fthe instrument housing to be passed downwardly and out of the lower end of the drill pipe. The operation of this embodiment will be substantially the same as that already described.

For a better understanding of the invention, reference may be had to the accompanying drawing in which Fig. 1 is a vertical, sectional view through a portion ofa bore hole showing a tool embodying the invention disposed Within a string of drill pipe; and

Fig. 2 is a View similar `to Fig. l but in which the tool is positioned below the drill pipe.

Referring to the drawing, a bore hole 10 is shown as having a drill pipe string 11 suspended therein. The upper end or portion of the bore hole ll may be provided with acasing 12 and the bore hole is shown as traversing among others two formations indicated at 14 and 16. Shown as suspended within the drill pipe 11 by means of a conductor cable 18 is'an elongated, sealed instrument housing 20. A drill bit 22 is shown diagrammatically as connected to the lower end of the drill pipe 11, and as is well known to those familiar with this subject, these drill bits are provided with openings through which drilling mud, indicated by the`arrows 24, can pass j, i

outwardly and then upwardly to the surface, through the annular space between the drill pipe and the walls of the bore hole. i

Within the lower portion of the housing 20 is shown a container of a suitable radioactive fluid, such as radioactive iodine, this fluid preferably being maintained under pressure within the container. A small tube or pipe 28 leads from the container 26 outwardly through the wall of the housing 2t) and this tube contains a valve 30 which may be opened and closed .by any suitable mechanism, such as a solenoid 32. The solenoid is connected through an electric battery 34 to a suitable actuating device which may comprise a clockwork mechanism 36.

A detector 38 of penetrative radiation, suchas a gamma ray counter, an ionization chamber or the like, disposed above the container 26 and far enough from the container to be out of range of the radiation from the material therein, say 5 or 6 feet, is connected through a preamplifier 40 to the lower end of the cable 1S. The preampliiied output from the detector passes upwardly over the cable lii which in turn passes over a drum 42 which may contain provision for measuring the amount of cable payed out, and thus the depth of the instrument within the bore hole. The cable 18 then passes to an amplifier 44, which is shown as connected to a suitable indicating means, or recorder 46.

In operation, when it has been found that circulation of the drilling mud 24 is being lost, the drilling operation is stopped, and the instrument 20 lowered through the drill pipe by means of the cable 18 to a position such as is shown in Fig. l of the drawing. The` circulation of the drilling mud 24 downwardly through the drill pipe is continued, and the clockwork mechanism 36 will have been previously set so that, after a time sufficient for the instrument to reach the bottom of the drill pipe, a circuit will be closed through the battery 34 and the solenoid 32 to operate the solenoid to open the valve 30 and thus release a small amount of the radioactive fluid from the container 26 into the drilling mud passing downwardly through the drill pipe. The drilling fluid indicated generally by the arrows 48 will therefore become radioactive.

Assuming that the formation 14 is sufhciently porous, the radioactive drilling mud will pass upwardly through the annular space around the lower portion of the drill pipe 11 and into the formation 14. The detector 38 being surrounded with this radioactive fluid will have its output increased, and this will be indicated at the indicating or recording device 46 at the surface. Assuming, however, that after the radioactive fluid has been injected into the stream of drilling mud, as has been described, the detector `38 does not show an increase in radioactivity, the operator at the surface will know that the radioactive drilling mud is not passing upwardly around the lower portion of the drill pipe, but rather, that it is passing downwardly into a porous zone or zone of lost circulation, such as is indicated at 16.

Assuming again that the radioactive fluid is passing upwardly into the zone 14, the drill pipe can be raised in the hole a few feet and the operation repeated. If the detector 38 still shows an increase in its response, the operator will know that the housing 20 is Still below the Zone of lost circulation 14, and he will again raise the drill pipe. Upon repeating the operation, the detector 38 may show no increase in its response upon injection of another quantity of the radioactive iiuid into the drilling mud stream 24, and the operator will then know that the drill bit and the apparatus is above the zone 14. By repeating this operation a few times, and by knowing the depth of the drill bit 22 or the instrument 20 in the hole, the operator can ascertain quite accurately the exact depth or position of the formation 14 within the bore hole.

in some instances the bit 22a (see Fig. 2) may be a core drill or a core drill bit, provided with a lower opening to permit a core to be cut and pass upwardly into the drill pipe lla. In this instance the instrument housing 20a may be lowered so that it will pass through the drill bit 22a and downwardly below the bit for a short distance. The instrument 20a is substantially the same as the instrument 20, which has been described with reference to Fig. l, and the operation will be substantially the same as that already described. The radioactive material injected into the drilling mud 24a would cause the mud to become radioactive, and if this mud passes downwardly and outwardly into a formation, such as indicated at 16a, the radiation detector will not show any increase in radioactivity, and the operator will know that the formation 16a is below the instrument 20a. If, however, the detectorv shows an increase in radioactivity, the operator will know that the radioactive mud is passing upwardly around the detector, and into an upper formation, such as that indi- Y cated at 14a.. With the tool below the drill bit, as described, detection of the radioactivity will be somewhat simplified since none of the radiation will be absorbed by the drill pipe.

lit is to be understood that instead of suspending the instrument 21B on a conductor cable, such as that indicated at 18, the instrument may, if desired, be self-contained. ln other Words, the output of the detector 38 may be recorded within the instrument housing 2t) by any suitable means, such as by passing the output from the preampliiier 4@ to a suitable recording device disposed within the housing. In this ease the power supply for the detector and the amplier and recorder would be taken from a battery similar to that indicated at 34, also disposed within the housing 20. An instrument of this type would be lowered on an ordinary cable and the mechanism 36 would be set to provide an ejection of the radioactive tluid into the mud stream at a predetermined time. The saine mechanism 36 may, if desired, control the operation of the recording device for the detector 38. The control mechanism 36 may be of a suitable type to provide for actuating the valve 30 and, if desired, a recorder contained within the housing 20, at intervals, between which the drill pipe can be raised or lowered so as to locate the porous formation, as has been described.

If desired, instead of utilizing the clockwork mechanism 36 for controlling the operation of the valve 30, this valve may be controlled from the surface as byconnecting the solenoid to the cable 18 and passing an energizing current down the cable.

Obviously, many other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. ln the process of drilling a borehole in which drilling fluid is pumped down through a string of drill pipe and out through the drill bit into the borehole and thence passes upwardly through the annulus between the drill pipe and the wall of the borehole, the method of locating a porous zone which has been drilled through and into which said drilling fluid is being lost which comprises injecting a given quantity of a tracer material into said drilling iluid at a point within the drill pipe yabove the drill bit, detecting the presence or absence of said tracer at a point in the borehole spaced vertically a constant distance above said injection point, the presence of the tracer in the annulus at the level of said detection point indicating that said porous zone is located at the level of said detection point or vertically spaced from said detection point at a still greater distance from the point of injection, and the absence of the tracer in the annulus at the level of said detection point indicating that` said porous zone is below the point of detection, then moving the point of tracer injection and the point of detection to a new elevation within the borehole while maintaining the constant distance between the point of injection and the point of detection, and repeating the foregoing steps.

2. The method described in claim l in which the tracer is a radioactive material.

3. In combination with a drill stem having a drill bit at its lower end position in a borehole, and means for circulating drilling fluid down the drill stem and out through the drill bit into the borehole for return through the 21m11.111s between the drill stem and the walls of the borehole, apparatus for locating a zone of lost circulation of the drilling iluid without removing the drill stem and the drill bit from the borehole, which comprises an elongated sealed housing, cable means suspending said housing within the drill stem above the bit, a quantity of a tracer lluid within said housing, means for injecting la slug of said tracer uid into said drilling uid at a point within the drill pipe above the drill bit, means within said housing for detecting the presence of said tracer in the drilling fluid passing up the annulus outside of said drill stem, said detecting means being spaced a fixed distance vertically above said injecting means, and means for changing the elevation of said housing with reference to said borehole, said injecting means having provisions for injecting a second slug of tracer uid into said drilling and out through the drill bit into the borehole and thence passes upwardly through the annulus between the drill pipe and the wall of the borehole, the method of locating a porous zone which has been drilled through and into which said drilling iuid is being lost which comlil) 6 pnses injecting a slug of a tracer material into said drilling uid at a point within the drill pipe above the drill bit, detecting the presence of said tracer material at a point in the borehole spaced vertically a constant distance above ysaid injection point, the presence of the tracer material in the annulus at the level of said detection point indicating that said porous zone is located at the level of said detection point or vertically spaced from said detection point at a still greater distance from the point of injection, then raising the point of tracer injection and the point of detection to a new elevation within theborehole while maintaining the constant distance between the point of injection and the point of detection, and repeating the foregoing steps until the absence of said tracer at the point in the borehole spaced vertically above said injection point is indicated.

References Cited in the rile of this patent UNITED STATES PATENTS 2,070,912 McDermott Feb. 16, 1937 2,315,355 Scherbatskoy Mar. 30, 1943 2,364,975 Heigl et al. Dec. 12, 1944 2,453,456 Piety Nov. 9, 1948 2,480,674 Russell Aug. 30, 1949 2,659,046 Arps Nov. 10, 1953 2,724,267 Bond et al. Nov; 22, 1955 

